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Safety and SIS · Glossary

What is Process Safety Time?

seconds or minutesSafety and SIS

Process safety time is the time from a process fault occurring until the hazardous event happens if no protective action is taken.

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Process Safety Time Explained

The SIF must detect the condition and bring the process to the safe state within this time. Its total response time includes sensor, logic, solenoid and valve stroke.

Many companies require the SIF response time to be well inside the process safety time, often no more than half.

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Calculators for Process Safety Time

CalculatorActuator Stroke Time CalculatorFree online calculator with formula and worked example.CalculatorPartial Stroke Test CalculatorFree online calculator with formula and worked example.

Frequently Asked Questions

What is Process Safety Time?

Process safety time is the time from a process fault occurring until the hazardous event happens if no protective action is taken.

Where does process safety time come from?

From process dynamics, for example how fast pressure rises after a valve fails closed.

Can a trip delay be used?

Only if the total response still fits within the process safety time.

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